The present invention is directed to aqueous absorption refrigeration or cooling systems in which water, as the sole refrigerant, is absorbed in an absorber by an aqueous absorption fluid, often referred to as a working fluid. Aqueous absorption fluids containing heat and mass transfer additives improve the absorption system performance by increasing water vapor absorption rates. For example, in U.S. Pat. Nos. 5,419,145 and 5,577,388, amines are shown to be effective additives for improving the performance of aqueous absorption fluids. The presence of such additives improves water cooling temperature changes in the absorber, increases the power load and heat and mass transfer, and reduces the observed process vapor pressure, as well as providing other advantages. The present invention describes other heat and mass transfer additives for improving performance of the systems in which the working fluids containing the additives are used.
According to the present invention, aqueous absorption working fluids are improved by adding effective amounts of an aliphatic, cycloaliphatic or aromatic ketone or aldehyde having between 5 and 24 carbon atoms. The improved heat and mass transfer additives are used in aqueous metal salt solutions. The presence of the effective amount of ketone or aldehyde increases the rate of water vapor absorption by the absorption fluid thereby achieving important advantages and improvements in system performance. The improvements include absorber power load increases and improvements in the change of absorber fluid concentrations. Further improvements include increases in overall heat transfer coefficients and sorption fluid side film heat transfer coefficients. The advantage of such improved absorption fluid performance allows for reduction of sorber heat exchange surface areas needed to satisfy a given load resulting in reduction of absorber size and costs. These and other improvements and advantages will be evident from the following detailed description.